1. Field of the Invention
Exemplary embodiments of the invention relate to a stereoscopic image display and a method for driving the same.
2. Discussion of the Related Art
A stereoscopic image display is divided into a display using a stereoscopic technique and a display using an autostereoscopic technique.
The stereoscopic technique, which uses a parallax image between left and right eyes of a user with a high stereoscopic effect, includes a glasses type method and a non-glasses type method. In the glasses type method, the parallax image between the left and right eyes is displayed on a direct-view display or a projector through a change in a polarization direction of the left and right parallax image or in a time-division manner, and thus a stereoscopic image is implemented using polarization glasses or shutter glasses. In the non-glasses type method, an optical axis of the parallax image between the left and right eyes is separated generally using an optical plate such as a parallax barrier and a lenticular lens, and thus the stereoscopic image is implemented.
U.S. Pat. No. 5,821,989 and U.S. Publication No. 2007022949A1 are known to disclose an example of the glasses type stereoscopic image display.
FIG. 1 schematically illustrates a glasses type stereoscopic image display. In FIG. 1, a black region of shutter glasses ST represents a shutter that blocks light traveling toward an observer (i.e., viewer), and a white region of the shutter glasses ST represents a shutter allowing transmission of light toward the observer. When a liquid crystal display element is selected as a display element DIS, a backlight unit providing light to the display element DIS is necessary.
As shown in FIG. 1, during odd-numbered frame periods, left eye image data RGBL is written to the display element DIS, and a left eye shutter STL of the shutter glasses ST is open. During even-numbered frame periods, right eye image data RGBR is written to the display element DIS, and a right eye shutter STR of the shutter glasses ST is open. Thus, the observer can view only a left eye image during the odd-numbered frame periods and only a right eye image during the even-numbered periods, thereby obtaining a stereoscopic feeling.
The display element DIS may display a two-dimensional image (hereinafter to as “2D image”) in a 2D mode and may display a three-dimensional image (hereinafter to as “3D image”) in a 3D mode. A vertical blank time, in which there is no data, increases in the 3D mode, so as to reduce 3D crosstalk, in which the observer may view an overlapping image of the left eye image and the right eye image. Alternatively, as shown in FIG. 2, there is a method for reducing a backlight turn-on rate of a liquid crystal display. The backlight turn-on rate indicates a rate of a turn-on time of the backlight unit BLU with respect to a fixed time. The backlight turn-on rate may be controlled by a pulse width modulation (PWM) signal capable of turning on and off light sources of the backlight unit BLU.
FIG. 2 illustrates a turn-on rate of the backlight unit BLU in the 2D and 3D modes.
As shown in FIG. 2, the light sources of the backlight unit BLU are turned on in a duty ratio of 100% in the 2D mode and are turned on in a duty ratio less than the 2D mode in the 3D mode. The backlight unit BLU is turned on for an open time of each of the left eye shutter STL and the right eye shutter STR of the shutter glasses ST. In the 3D mode, the left eye shutter STL of the shutter glasses ST is open when the left eye image is displayed on the display element DIS, and the right eye shutter STR of the shutter glasses ST is open when the right eye image is displayed on the display element DIS. However, because the backlight unit BLU is turned on in the low duty ratio in the 3D mode, the user feels that a luminance of the stereoscopic image display in the 3D mode is less than the 2D mode.